1. Field of the Invention
This invention broadly relates to apparatus and methods for applying orthodontic adhesive to orthodontic appliances that are bonded to the patient's teeth. More particularly, the present invention relates to apparatus and methods for applying orthodontic adhesive to appliances used in indirect bonding procedures, such as appliances connected to indirect bonding trays or jigs.
2. Description of the Related Art
Orthodontic treatment involves movement of malpositioned teeth to desired locations in the oral cavity. Orthodontic treatment can improve the patient's facial appearance, especially in instances where the teeth are noticeably crooked or where the jaws are out of alignment with each other. Orthodontic treatment can also enhance the function of the teeth by providing better occlusion during mastication.
One common type of orthodontic treatment involves the use of tiny, slotted appliances known as brackets. The brackets are fixed to the patient's teeth and an archwire is placed in the slot of each bracket. The archwire forms a track to guide movement of teeth to desired locations.
The ends of orthodontic archwires are often connected to small appliances known as buccal tubes that are, in turn, secured to the patient's molar teeth. In many instances, a set of brackets, buccal tubes and an archwire is provided for each of the patient's upper and lower dental arches. The brackets, buccal tubes and archwires are commonly referred to collectively as “braces”.
In many types of orthodontic techniques, the precise position of the appliances on the teeth is an important factor for helping to ensure that the teeth move to their intended final positions. For example, one common type of orthodontic treatment technique is known as the “straight-wire” technique, where the archwire lies in a horizontal plane at the conclusion of treatment. Consequently, if a bracket is attached to the tooth at a location that is too close to the occlusal or outer tip of the tooth, the orthodontist using a straight-wire technique will likely find that the tooth in its final position is unduly intruded. On the other hand, if the bracket is attached to the tooth at a location closer to the gingiva than is appropriate, it is likely that the final position of the tooth will be more extruded than desired.
In general, orthodontic appliances that are adapted to be adhesively bonded to the patient's teeth are placed and connected to the teeth by either one of two techniques: a direct bonding technique, or an indirect bonding technique. In the direct bonding technique, the appliance and adhesive are grasped with a pair of tweezers or other hand instrument and placed by the practitioner on the surface of the tooth in an approximate desired location. Next, the appliance is shifted along the surface of the tooth as needed until the practitioner is satisfied with its position. Once the appliance is in its precise, intended location, the appliance is pressed firmly onto the tooth to seat the appliance in the adhesive. Excess adhesive in areas adjacent the base of the appliance is removed, and the adhesive is then allowed to cure and fix the appliance firmly in place.
While the direct bonding technique described above is in widespread use and is considered satisfactory by many, there are shortcomings that are inherent with this technique. For example, access to surfaces of malposed teeth may be difficult. In some instances, and particularly in connection with posterior teeth, the practitioner may have difficulty seeing the precise position of the bracket relative to the tooth surface. Additionally, the appliance may be unintentionally dislodged from its intended location during the time that the excess adhesive is being removed adjacent the base of the appliance.
Another problem associated with the direct bonding technique described above concerns the significant length of time needed to carry out the procedure of bonding each appliance to each individual tooth. Typically, the practitioner will attempt to ensure that each appliance is positioned in its precise, intended location before the adhesive is cured, and some amount of time may be necessary before the practitioner is satisfied with the location of each appliance. At the same time, however, the patient may experience discomfort during the procedure and have difficulty in remaining relatively motionless, especially if the patient is an adolescent. As can be appreciated, there are aspects of the direct bonding technique that can be considered a nuisance for both the practitioner and for the patient.
Indirect bonding techniques avoid many of the problems noted above. In general, indirect bonding techniques known in the past have involved the use of a placement device having a shape that matches the configuration of at least part of the patient's dental arch. One type of placement device is often called a “transfer tray” and typically has a cavity for receiving a number of teeth simultaneously. A set of appliances such as brackets are releasably connected to the tray at certain, predetermined locations.
Other types of placement devices used in indirect bonding are often referred to as “jigs” and resemble a framework that contacts one or more teeth at certain locations. For example, a jig constructed for use in bonding a single appliance to a single tooth may have an arm that extends over and contacts an incisal section of the tooth. An appliance such as a bracket is releasably connected to the jig at a certain, predetermined location relative to the tooth.
During the use of orthodontic placement devices for indirect bonding, an adhesive is typically applied to the base of each appliance by the orthodontist or a staff member. The placement device is then placed over the patient's teeth and remains in place until such time as the adhesive hardens. Next, the placement device is detached from the teeth as well as from the appliances, with the result that all of the appliances previously connected to the placement device are now bonded to respective teeth at their intended, predetermined locations.
Indirect bonding techniques offer a number of advantages over direct bonding techniques. For one thing, and as indicated above, it is possible to bond a plurality of appliances to a patient's dental arch simultaneously, thereby avoiding the need to bond each appliance in individual fashion. In addition, the placement device helps to locate the appliances in their proper, intended positions such that adjustment of each appliance on the surface of the tooth before bonding is avoided. The increased placement accuracy of the appliances that is often afforded by indirect bonding techniques helps ensure that the patient's teeth are moved to their proper, intended positions at the conclusion of treatment.
In recent years, many improvements have been made in the field of indirect bonding. For example, U.S. Pat. No. 5,971,754 (Sondhi et al.) describes a two-component indirect bonding adhesive with a relatively fast curing time that reduces the length of time that the tray must be firmly held against the patient's teeth. U.S. Pat. No. 6,123,544 (Cleary) describes a transfer tray that receives movable arms for placing appliances on the patient's teeth once the tray is positioned in the oral cavity. U.S. Pat. No. 7,020,963 (Cleary et al.) describes among other things a transfer apparatus with an improved matrix material for releasably holding appliances in place. Published U.S. Patent Application No. 2005/0074716-A1 (Cleary et al.) describes a placement device with appliances that are precoated by the manufacturer and received in a container for convenient use by the practitioner when desired.
A wide variety of orthodontic adhesives are available, and some practitioners prefer to use orthodontic adhesives with relatively low viscosities. However, low viscosity adhesives pose difficulties when precoated onto the base of appliances by the manufacturer. For example, the adhesive may not be sufficiently stiff to enable the adhesive to retain its shape and stay in its proper place on the base of the appliances during shipping and handling of the container and until such time as the container has been opened by the practitioner.
In addition, there is a continuing need to improve the state of the art of indirect bonding so that the practitioner's time in completing the bonding procedure is reduced. Such a reduction in time may also serve to benefit the patient since the amount of chair time is reduced as well.